The requirements for the capabilities of cruise control testers have changed over a period of time due to the changes made by vehicle manufacturers in the cruise control system itself and its adaptation to various models of vehicles. It is not cost effective to produce a new tester each time a change requirement occurs. Accordingly, it is desirable to provide a cruise control tester which is adaptable to modification for changing its capabilities to meet new requirements.
A particular cruise control tester known as Model CTI-232 has been marketed for several years by Concept Technology, Inc. of Birmingham, Mich. This tester functions on General Motors cruise control systems on 1982 to 1997 model vehicles and beyond. This tester will test the new Electromotor II, Electromotor I, Custom Cruise III (high frequency) Systems. With adapters, it will test the Custom Cruise Control III (low frequency) Systems. The tester uses two sets of connectors which allows the tester to be connected between the vehicle harness and the cruise control module. This tester is actually two testers in one; the first part tests the vehicle harness while the second part tests the control module. It is a hand-held tester and will conduct a complete test of components on the different cruise control systems without starting the engine.
The "Cruise Lamp" on the prior art tester originally tested the "Cruise Engage" lamp on the vehicle instrument panel. If the vehicle used a "Cruise Engage" lamp the tester would test it for continuity. If the vehicle did not use a "Cruise Engage" lamp, the tester "Cruise Engage" lamp would not light. Therefore only two scenarios existed, vehicles with and vehicles without "Cruise Engage" lamps on the instrument panel. Now a third scenario exists, that is a vehicle having a "Cruise Engage" control wire connected to the vehicle Powertrain Control Module (PCM). The PCM controls all the drive train functions of the engine, transmission and any other computers that might be used in the drive train configuration. The PCM also communicates with the instrument panel electronics to report road speed and other engine data. It is through this wire that the cruise control module tells the PCM that the cruise system is "Engaged". The input impedance characteristics of this PCM input are not compatible with the tester input. When the tester is connected to a vehicle where the "Cruise Engage" wire is connected to the PCM, the "Cruise Engage" lamp lights only very dimly which causes misdiagnosis by the technician.
This invention modifies the well known CTI 232 tester to allow it to function on the latest versions of the General Motors Delphi Cruise Control Systems.
A general object of this invention is to overcome certain disadvantages of the prior art and to provide an improved cruise control tester with the capability of testing new model cruise control system on new vehicle models.
A complete understanding of this invention may be obtained from the detailed description that follows taken with the accompanying drawings.